1. Field of the Invention
The present invention relates to an aqueous ink or set of inks for printing uncoated vinyl foils or substrates which are coated with vinyl. The present invention also relates to a method of using the ink.
2. Description of the Related Art
Inks for printing foils are known in principle.
When printing vinyl foils, it is necessary to distinguish between the coatings of coated and uncoated foils.
For printing uncoated foils, special inks on a non-aqueous basis are known, wherein these inks are also referred to as so-called solvent inks.
These inks have the disadvantage that they have a strong and unpleasant odor, are damaging to health and are flammable. This is also partially true for so-called ECO-solvent inks or light-solvent inks. Another disadvantage is to be seen in the fact that solvent inks can only be used in so-called solvent printers which are very expensive. There is no doubt that the above-described solvent inks dissolve the substrate and partially or fully roughen the substrate, so that the dried printed line has a good resistance to stretching.
The use of solvent printers has the disadvantage that these printers have a large structural size because due to the use of organic solvents, such as butylglycol acetate, suction installations or encapsulations must be provided for protecting the operating personnel. In addition, solvent printers are more expensive than printers for aqueous systems because the components used in the systems, such as hoses, must be resistant to organic solvents.
In addition, special foils can be printed with conventional aqueous inks if the vinyl foils are provided with a coating or a rough surface or are otherwise roughened.
However, the decisive disadvantage is the fact that the foils having special coatings are always extremely expensive. The special coatings have a rough surface and a defined porosity in order to impart a good resistance to scratching to the printed images or lines produced with aqueous inks on such foils.
In addition, EP 0 974 626 A1 discloses an aqueous pigment ink for printing uncoated vinyl substrates. This ink is composed of an aqueous carrier medium, a drying decelerator, a coloring agent which cannot be dissolved, a dispersing agent and a wetting agent. Such ink has the disadvantage that it does not dry well because of the high proportion of drying decelerator on the basis of glycols. In addition, after printing, the inks have the tendency to blur or even smudge. The printed images must be dried after the printing process at high temperatures. Moreover, it has been found to be disadvantageous that these inks are only resistant to scratching after a complicated drying process at temperatures of about 200° C.
For drying the printed images produced in the above-described manner, printers with heating devices are known in the art. The heating devices are constructed essentially plate-shaped and arranged in such a way that the substrate to be printed upon slides over the surfaces of the plates in order to heat the substrate. The printing process is followed with respect to location and time by another heating zone which dries the printed ink. The disadvantage of printers constructed in this manner is the fact that two heating zones are necessary for safely drying the ink on the substrate.